My invention relates generally to cardiac stimulation, and more particularly to a system for removing an implanted endocardial pacemaker lead or an implanted transvenous defibrillation lead from the heart.
Various factors affect the human heart rate and contribute to changes of rate from what is termed the normal sinus rate range (rates generally ranging in adults from 60 to 100 beats per minute). In healthy persons, tachycardia (100 to 160 beats per minute) is experienced as a result of such things as physical or emotional stress (exercise or excitement), consumption of alcoholic or caffeinated beverages, cigarette smoking, or ingestion of certain drugs. Variation from normal sinus rate range is generally characterized as cardiac arrhythmia, and arrhythmia rates exceeding the upper end of the sinus rate range are termed tachyarrhythmias. Arrhythmia rates below the normal sinus rate range are termed bradycardia.
Arrhythmias typically arise in the atria or ventricles as a consequence of an impairment of the heart's electrical electro-physiologic properties such as excitability, conductivity, and automaticity (rhythmicity). Such arrhythmias require special treatment. Cardiac pacemakers, chronically implanted within the patient's body, and connected to the heart by one or more leads, are frequently used to control bradycardia conditions. Implantable cardioverter-defibrillators, also implanted chronically in the patient's body and connected to the heart by one or more leads, can be used to control tachyarrhythmias, life-threatening or not, and life-threatening fibrillations.
There are generally two types of body implantable leads used with cardiac pacemakers--one which requires surgery to expose the myocardial tissue whereby an electrode is affixed to the epicardial tissue and another which can be inserted through a body vessel, such as a vein, into the heart where an electrode contacts the endocardiac tissue. In the latter type, the endocardial lead is often secured to the heart through the endothelial lining by a helix affixed to a distal end of the lead. When the end of the lead contacts the lining of the heart at a desired location, the lead may be secured in place by rotating the lead, thus screwing the helix into the heart tissue. Other types of active or passive fixation have also been used to secure the lead to the inner wall of the heart, such as hooks or tines.
Similarly, cardioverter defibrillators have used both epicardial leads, that is, leads with electrodes attached to the outside of the heart, and endocardial leads, that is, leads inserted into the heart through a body vessel. One such endocardial lead, is described in U.S. Pat. No. 4,922,927 to Fine, et al., assigned to the assignee of my invention.
With either pacing or defibrillation endocardial leads, fibrotic tissue may eventually encapsulate the lead, especially in areas where there is low velocity blood flow. When small diameter veins through which the lead passes become occluded with fibrotic tissue, separating the lead from the vein is difficult and can cause severe damage to or destruction of the vein. Furthermore, separation may not be possible without constricting or containing the movement of the lead.
In most cases, an endocardial lead will outlast its associated implanted device. However, the lead may become inoperative or another type of lead may be required. Frequently, the existing lead is left in place and an additional lead is implanted, rather than risk removal of the old lead, now bonded to the surrounding tissue. Leaving the implanted lead in place, however, particularly in the heart, may further restrict the operation of various heart valves through which the lead passes. If several leads are left in place, the operation of the heart and its efficiency may be impaired.
In addition, infection may occasionally develop in or around a lead, requiring surgical removal. In some cases, surgical removal may involve open heart surgery with its accompanying complications, risks, and costs. These risks are significant for the endocardial pacemaker lead. Because the endocardial defibrillation lead is larger and more complex, the complications associated with the removal of a defibrillation lead can be even greater.
Several methods for removal of pacemaker leads have heretofore been proposed. One method involves a lead removal tool that utilizes a hollow, rigid tube and a beveled rod tip for engaging and deforming the coil structure of the heart lead. However, if such a lead could not be removed because of some complication, the tip of the tool was nevertheless locked in place and could not be removed from the lead. Consequently, both the tool and the lead would have to be surgically removed. Moreover, the rigid tube of the tool could easily puncture a blood vessel or a heart cavity wall.
Another method for transvenously extracting a lead involved manual manipulation without the add of a tool. Such a method is not possible if the lead has become encapsulated in a blood vessel. Moreover, the method puts excessive strain and tension on the polyurethane or silicone insulation surrounding most pacemaker leads. Should the lead break, the broken inner coil and insulation could damage the heart or surrounding blood vessels. Surgical removal of the broken lead would be imperative. Moreover, if the pacemaker lead included times, a cork screw, or other fixation device at the tip, pulling on the lead could seriously damage the wall of the heart.
Another technique has been proposed by Cook Pacemaker Corporation, and is described in a series of U.S. Patents to Goode, et al., beginning with U.S. Pat. No. 4,943,289. This method generally includes the use of a stiffening stylet which can be inserted into the lead and which engages the inner coil of the lead near the tip, allowing tension to be applied through the stiffening stylet close to the tip of the lead. The technique also uses a pair telescopic flexible tubes which are slid over the lead to free fibrotic connections until the tubes are close to the distal tip of the lead.